Signaling system



L. W. AUSTIN SIGNALING SYSTEM Aug. 24

Filed June 22, 1923 2 Slwets--Sheev Patented Aug. 24, 1926.

UNITED STATES LOUIS W AUSTINZ-OF WASHII Q'GTON, DISTRICT OF COLUMBIA.

SIGNALING SYSTEM.

Application filed lung 22, 1923. Serial No. 647,058.

My invention relates broadly to signaling systems, and more particularlyto means for reducing undesired oscillations and interfering frequenciesin si naling circuits.

One of the'objects- 0 my invention is to provide means for increasingthe sharpness of tuning in signaling circuits and to decreaseinterference when utilizing a predetermined frequency due tosimultaneous sig naling at closely adjacent frequencies.

Another object of the invention is to provide a circuit arrangement bywhich rejector circuits may be coupled with a signaling system in suchmanner that inherent losses heretofore involved in rejector circuits areeliminated.

My invention finds particular application in radio signaling circuitsboth at the transmitter and at the receiver. The sharpness in tuning isincreased and the tendency of the circuits to oscillate on harmonics orundesired frequencies is considerably reduced.

My invention accomplishes these results by providing means forcontrolling the radio frequency oscillations at either the transmitteror receiver so that those of the predetermined desired frequency shallbe forced into the active portions of the circuits while those of otherfrequencies shall beby-passed and rendered harmless to act upon suchportions of the circuits. Y

My invention comprises broadly a coupled circuit arrangement in which aninductive member of normally small impedance for a broad band offrequencies is made of high impedance for a particular frequency bybeing closely coupled to a closed circuit containing a relatively smallcapacity and a comparatively large inductance, tuned to the particularfrequency while remaining low in its effective impedance for all otherfrequencies. When this particular frequency is chosen as the desiredsignaling frequency and the circuit associated with the signalingcircuit the particular frequency will be forced back or rejected by theassociated circuit to be actively employed in the signaling circuit,whereas all other frequencies may pass through the associated circuit.

My invention will be more clearly understood by reference to theaccompanying drawings. in which:

Figure 1 is a wiring diagram showing a portion of the signaling circuitwith the circuit of my invention associated therewith;

Figure 2 is a wiring dia am of an antenna ground circuit showing t ecircu t of my invention connected at a nodal point in the antenna groundcircuit; Figure 3 is a. wiring diagram showing a plurality of thecircuits of my invention employed in connection with an antenna groundsystem; Figure 4 shows the application of my invention to a closedelectrical circuit intermediate the radio fre quency energy collectingcircuit, which may be a coil antenna or an antenna ground sys tem anddetecting circuit in the case of reception, or the circuit containingthe source of oscillations in the case of transmission; Figure 5 showsthe application'of my invention to a transmitting antenna system foreliminating harmonics and other undesired frequencies; and Fi ure 6 is awiring diagram showing a plurality of the'devices of my inventionapplied to a signaling circuit for a transmitter.

Referring more particularly to Figure 1 of the drawings, the inventionis shown applied to an antenna ground system indicated by referencecharacters 1 and 2. Inductance 3 and capacity 4 are included in thiscircuit forming the usual tuned oscillatory system. An inductance 5composed of a small number of turns with very small inductance ascompared with inductance 3 is included in a circuit 6, which circuit isin parallel with the tuned circuit 34. The inductance 5 is of such valuethat ordinarily all frequencies pass through the circuit 6 in preferenceto passing through the circuit 3l. A closed circuit represented byreference character 8 is employed, the circuit comprising an inductance10 and a variable capacity 9. The inductance 10 is closely coupled tothe small inductance 5. lVhen the circuit 8 is tuned to any givenfrequency the effective impedance of the small inductance 5, which isextremely low for all frequencies, increases to a high value for thefrequency to which the circuit 8 is tuned while remaining low for allother frequencies. Vhen the circuit 8 is tunedto the same frequency asthe circuit 34 then this particular frequency will be forced back orrejected by inductance 5 and circuit 6, and will flow practicallyentirely through 34 while other frequencies will be bypassed through thecircuit 6. The antenna ground circuit 12 and C1ICl1ll3 34: is en ergizedin the case of a transmitter by cirpoint and tuning inductance 18 andcondenser 19 when coupled directly to the systern 12 includinginductance 14 and capacity 15. Next the ground connection at 16 isremoved and with the circuit arranged as represented in Fig.2.Inductance 3 and capacity 20 are tuned, while coupled to the system 12by means of inductances 14 and 3 without in any way changing thesettings of inductance 18 and capacity 19. In this arrangement thedesired frequency will be more completely rejected by circuit 5 andaccepted by the circuit 34 while other frequencies are more completelyby-passed through inductance 5.

Greater selectivity is obtainable by increasing the number of the'rejectors as represented in Fig. 3. In this circuitthe antenna system1-2 contains nodal points 16 and 21 fixed by a method similar to thatdescribed in connection with Fig. 2. The antenna ground circuit 1-2includes the ad- 'ditional tuning condensers 22. 23. and the inductance24 and capacity 25. The additional circuit 26 is included between nodalpoints 21 and the ground 2, the circuit comprising small inductance 27which normally passes a. wide band of frequencies. A closed circuit 28containing inductance 30 and capacity 29 is inductively associated withinductance 27. Greater selectivity is obtained by adjusting bothcircuits Sand 28 to the signaling frequency, whereupon this frequency isforced back or rejected by circuits 6 and 26, causing the desiredfrequency to be confined to the antenna ground circuit while undesiredfrequencies are by-passed by the auxiliary circuits 6 and 26.

In Fig. 4 my invention is illustrated as applied to a closed circuitconnected with inductance 14 which .may be coupled with the antennaground circuit 1234. The circuit is positioned intermediate the antennaground system and the circuit 31, which in the case of the transmitteris connected to a source of oscillations, or in the case of a receiverto a detection or amplification system. The intermediate circuitcomprises coupling coils 14 and 32 and condensers 33 and 34. At nodalpoints 35 and 36 in the ,intermediate circuitv I connect the smallinductance coil 5 and the circuit 8 containing inductance 10 andcapacity 9. In this-arrangement the coupled rejector by-passes theundesired frequencies and forces the desired frequency through theinductance 32 in the case of a receiver'from whence it is passed throughinductance 37 and condenser 38 to the amplification or detectioncircuit. In the case of a transmitter the desired frequency is forcedinto inductance 14 and undesired harmonics are substantially eliminated.

The principle of my invention is applicable to a transmitting antennafor eliminating harmonics generated by the source of oscillations asrepresented in Fig. 5. The system may comprise an arc generator 40 inthe antenna ground circuit 1'-2 in series with inductances 4142 andcapacity 43. At a nodal point 44 I connect a circuit around theoscillating arc circuit to a point 45 including the small inductance 46which is coupled to the tuned circuit 47 including inductance 48 andcapacity 49. By tuning the circuit 47 to the signaling fre uency' theinductance 46 becomes a high e ective impedance for the signalingfrequency while by-passing harmonics, and eliminating interferenceresulting from harmonic'radiation.

Fig. 6 represents an application of my invention to. the control ofcurrents in a transmitting antenna so that the current may be made toflow either to the antenna or into an artificial antenna 58. The antennaground circuit 12 is so tuned that 44 is a potential node and the smallinductances 50 and 51 in the antenna and the artificial antenna circuitare coupled respectively to the closed circuits 52 and 53 which arenormally tuned-to the frequency being emitted by the station, and arerespectively detuned' by closing the keys 5455 across a'portion of therespective inductances 56 and 57. By alternately tuning one of therejector circuits while the other is detained, the current will bealternately forced into the antenna or into the artificial antenna. Bythi'sarrangement the keys 54 and 55 operate practically without sparkingsince when they are closed practically no current is flowing in theirrespective circuits 51 and 52. At the same time harmonics and otherundesired frequencies will always flow by preference through theartificial antenna. If desired, delayed opening keys 54 and 55 can beused to open the respective circuits after the main current has beensuppressed by the coupled rejectors.

The principle of operation of my inven tion has been already discussed,but it miriht be pointed out that the broad operating principle is thatI provide a path or several paths in connection with a signaling circuitwhich are normally transparent to a broad band of frequencies. Theeffective impedance of the path or paths is then increased in value forthe particular signaling frequency whereby the signaling frequency isconfined to the signaling circuit and the path or paths are renderedsubstantially opaque to the signaling frequency while all otherfrequencies may pass freely through the transparent path or paths. I amenabled to utilize a comparatively small capacity and a relatively largeinductance by my coupled rejectors thereby reducing losses heretoforeinherent in prior forms of rejectors.

While I have described my invention in certain specific embodiment, itwill be understood that I intend no limitations other than are imposedby the scope of the appended claims.

Having thus described my invention, what I claim and desire to secure byLetters Patent of the United States is: i

1. A signaling s stem, com bination a signa 'ng circuit, means fortuning said circuit to the signaling freuency, a second circuitcontaining a coil e ectrically connected with said signaling circuit andnormally transparent to a broad band of frequencies, and meansinductively associated with said last mentioned circuit whereby saidsecond circuit is rendered opaque to the signaling frequency buttransparent to other requencies, causing said signaling frequency to beconfined to said signaling circuit and all other frequencies to bebypassed by said second circuit, said means inc uding a coil containinga greater number of turns than the first mentioned coil.

2. In a signaling system, the combination of a signaling circuit, meansfor tuning said signaling circuit to a particular signalin frequency,a,,pluralit of paths each containing a coil electrica ly connectedwithsaid signaling circuit and arranged to be normally transparent to abroad band of frequencies, and independent means inductively connectedto each of said paths whereby said paths are rendered opaque to theparticular signaling frequency but transparent to all other frequencies,said means including a coil containing a greater number of turns thanthe first mentioned coil.

3. In a signaling system, the combination of a signaling circuit, aplurality of means for tuning said circuit to a particular signalingfrequency, a plurality of circuits prising in comconnected to saidsignaling circuit and separately connected to nodal points along saidsignaling circuit and between said first men tioned means, saidcircuitsbeing normally transparent to a broad band of fre uencies, and separatetuned circuits couple therewith ,whereby said circuits are renderedsubstantially opaque to said signaling frequency, forcing said signalingfrequency into said signaling circuit and by-passing all otherfrequencies.

4. A- signaling system, comprising in I combination a signaling circuit,inductive and capacitive means for tuning said circuit to the signalingfrequency, a second ing a relatively small capacity and a relativelylarge inductance coupled with said "last mentioned inductance wherebysaid second circuit is rendered opaque to the signaling frequency buttransparent to other frequencles, causing said signaling frequency to beconfined to said signaling circuit and all other frequencies to beby-passed by said second circuit.

5. In a signaling system, the combination of a signaling circuit,inductive and capacitive means for tuning said signaling circuit to aparticular signaling frequency, a plurality of paths electricallyconnected with said signaling circuit each containing an inductancesmall in value as compared with said inductive means and each arrangedto be normally transparent to a broad band of frequencies, andindependently tuned circuitscoupled to each of said inductancescomprising relatively small capacities and relatively large inductancesarranged to be tuned to said signaling frequency whereby said paths arerendered opaque to the particular signaling frequency but transparent toall other frequencies.

6. The combination of a signaling circult, means for tuning the saidcircuit to a particular signaling frequency, a path containg ing a coilresponsive to a broad band of fresaid last mentioned meansincludingatransthe voltage transformation ratio of former, which isother than unity.

8. A signaling system comprising the combination of a signaling circuit,means for tuning said circuit to the signaling frequency, a secondcircuit containing a coil electrically connected with said signalingcircuit and normally transparent to a broad band of frequencies, andmeans inductively associated with the last mentioned circuit wherebysaid second circuit is rendered opaque -to the signaling frequency, saidmeans including a condenser connected across a coil which contains agreater num ber of turns than the first-mentioned coil.

9. In a signaling system, the combination of asignalingcircuit, meansfor tuning said signaling circuit to a particular signaling frequency, aplurality of paths each containing a coil electrically connected withsaid signaling circuit and arranged to be normally transparent to abroad .band of frequencies and independent means inductively connectedto each of said paths where-' by said paths are rendered opaque to theparticular signalling frequency but transparent to allother frequencies,said means including a condenser connected across a coil which containsa eater number of turns than the first mentioned coil.

10. A signaling system comprising in combination a signaling circuit,means for tuning the circuit to the signaling frequency, a coilconnected in parallel with said circuit, said coil comprising theprimary of a transformer, the secondary of which consists of a coilcontaining a number of turns greater than that in the primary, and anadjustable condenser connected across the secondary.

LOUIS W. AUSTIN.

